The present invention relates generally to the storage and retrieval of multimedia information in a high speed ATM networking environment and more particularly to an input-output device that can be used as a multimedia server add-on to an existing personal computer or workstation.
One trend in personal and business computer systems is to provide the capability to send and receive multimedia data. Multimedia data includes audio, video, graphics, and facsimile as well as data files. These different types of multimedia are also referred to as diverse data objects, DDO. If these diverse data objects must be transmitted or received without perceptible delay to the user, the application requires real time data transmission, referred to as real time DDO. Traditional data services such as file transfer or electronic mail generally do not require real time data transmission. However, multimedia applications that integrate digital audio and video require certain minimum transmission times in order to provide the user the type of response (real time) that the user is accustomed to receiving. Users of multimedia services will not tolerate delays or interruptions in voice or video due to throughput delays on a communications network.
One critical element that comprises a typical communications service interface is the Quality of Service (QoS). A given communications system has defined QoS parameters that may include communications link setup time, end-to-end delay, data loss probability, and synchronization. From a user perspective, a guaranteed QoS means the reception of multimedia without perceptible delay or interruptions. Thus full motion video requires a higher QoS than electronic mail since electronic mail is a non-real time DDO and full motion video is a real time DDO. In essence, QoS is another name for network bandwidth management. Certain applications that are multimedia intensive require larger amounts of dedicated bandwidth in order to provide a guaranteed Quality of Service to the network user.
Multimedia data is often transmitted over some type of communications network. Typical networks include local area networks (LANs) such as Ethernet or FDDI, or wide area networks (WANs) such as the Internet or Integrated Services Digital Network (ISDN). Personal computers and workstations with multimedia capability can connect to a communications network to transmit and receive diverse data objects.
The trend in networking technology is toward broadband integrated communications networks designed for bit transmission rates ranging from megabits to gigabits per second. A predominant driving force behind this trend is the large amount of digital data bandwidth needed to represent and transmit video and graphics data objects.
The broadband integrated services digital network (B-ISDN) is designed to support the high data rates necessary to transmit real time DDO. B-ISDN uses a type of data transfer known as asynchronous transfer mode (ATM) to transport data in blocks of data referred to as cells. ATM data transmission will likely take place over fiber optic networks due to the high data speeds and favorable wide transmission bandwidths of fiber optics. International standards are in place for high speed data transmission over fiber optics using a synchronous optical network referred to as SONET. SONET is a network service capable of delivering multiple channels of data from various sources in transmission rates that start at an optical carrier (OC) rate of 51.84 Mbps. Thus OC-1 is 51.84 Mbps. Two standard high speed SONET networks proposed are OC-3 at 155.52 Mbps and OC-12 at 622.08 Mbps. Since SONET networks will carry multimedia voice, video, and image as well as traditional data, the basic unit of 8-bit measure is referred to as an octet rather than a byte. In summary, SONET and ATM architectures are used in combination as part of the overall broadband ISDN network.
Workstations and personal computers have evolved with faster and larger semiconductor microprocessors and memories to be able to process the large amounts of digital data. The use of improved bus architectures including MCA, PCI, and ISA has also improved the data handling capabilities of personal computers and workstations. But even with the improvements in microprocessor, memory, and bus technology, it places a high demand on computer resources each time a multimedia application or stream of diverse data objects is transmitted or received by a computer system. The demands on a personal computer or workstation to process information increase once a connection is made to a high speed network such as broadband ISDN. This is particularly true if the primary data bus is used both for microprocessor communications to memory and I/O and external multimedia communications.
A direct connection to a high speed communications network is common for low speed applications using traditional analog modems and predominately non-real time applications. Traditionally, an optional communications card can be purchased for a PC or workstation to allow single user point-to-point communications. A major drawback of this approach, however, is that the add-on card uses the computer system bus for communications. Although acceptable at kilobit data transmission rates, true high speed transmission is extremely difficult using this approach.
In addition, it is useful in high speed networks to be able to manage Quality of Service requirements and multimedia transmission or reception requests with some type of communications server. Communications servers are devices connected to a given LAN or WAN network in order to manage communications. Traditional communications server functions include connection of one or more personal computers or workstations to a network, allocation of a channel or bandwidth for communications, and the ability to temporarily store data until it can be processed by the personal computer or workstation. A communication server can also be used to store multimedia for broadcasts retransmission to multiple users.
Heretofore, a dedicated server using dual state of the art Intel Pentium processors configured using NT server architecture is unable to support full speed ATM OC-3 data transmission speeds. It is therefore desirable to provide a method and architecture to relieve the host computer processor and memory of the responsibilities traditionally associated with network card interface support in order to construct a multimedia communications server capable of ATM speeds at OC-3 and higher data rates.
Most communication servers are dedicated servers, that is, they are dedicated to only the performance of communications management functions. A traditional multimedia server cannot be used as a personal computer or workstation, and in addition can be a costly component to add to a local area network.
The ability to match the amount of computing power, data bandwidth, or communication processing capacity to the amount needed for a given task is commonly referred to as scalability. When referring to the amount of data transmission bandwidth required for a given application, this scaleable concept is often referred to as bandwidth on demand. Thus when only a small amount of data must be transmitted over a computer network, only the amount of network bandwidth necessary to transmit the data is allocated to the application. Partitions of network capacity are called channels, and as an application's bandwidth requirements increase, the network can allocate more channels to that application.
Multimedia applications lend themselves well to scaleable network architectures. Scalability refers to the ability of distributed processing systems to add clients without degrading the overall performance of the system. For example, a host communications server can be used to provide for a scaleable number of simultaneous streams (playback) of a single copy of an object. One good example of this is video on demand. A multimedia server may have several hundred full length video movies stored in its memory. If a user were to demand from the network to view a given movie, a channel could be allocated to playback a single copy of the movie (object). As more users demanded to see the same movie, the communications server could then provide additional channels of video data as needed. In this manner, the multimedia server is scaleable.
Therefore, there is a need for a low cost solution for transforming a traditional personal computer or workstation into a high speed ATM multimedia server while preserving the personal computer or workstation functionality.